Gas analyzers are typically used in a variety of applications to measure the quality of air at a plant site, such as by way of example, a petrochemical plant or a coal plant. These gas analyzers are used to detect the presence of trace amounts of pollutants or impurity gases. By way of example, industrial hygiene and EPA emission applications commonly require measuring air quality with the use of gas analyzers.
The gas analyzers periodically require the use of calibration gases as an integrity check to ensure the analyzers are properly functioning. The calibration gases contain precise amounts of the gases to be detected (e.g., hydrogen sulfide, carbon monoxide and combustibles) by the gas analyzer, and as such are generally used to verify whether the gas analyzers are calibrated and functioning properly. The calibration gases are commonly provided as a compressed gas in high pressure cylinders (e.g., 500-1000 psig). The gas compressed cylinders can contain precise amounts of calibration gases such as, by way of example, hydrogen sulfide (H2S), carbon monoxide (CO) or combustibles. The calibration gases are generally used for the calibration and/or “bump” checking of portable and fixed air/gas monitors. The term “bump” test or check is a method that generally involves delivering a calibrated gas mixture to gas monitoring equipment to verify the response of the gas monitoring equipment. The response can occur by any suitable means including an audible response or a visible response. Additionally, portable user-worn gas monitors generally employ a vibratory alarm response. The monitors can be used to measure percent oxygen; % lower explosive limit (LEL); and parts per million concentrations of hydrogen sulfide, ammonia, and other gases.
The compressed gas cylinders which contain the calibration gases are typically required to be relatively small in size, lightweight and portable to be conducive for usage at various locations on a plant site. In order to achieve these attributes, the compressed gas cylinders typically have a water volume of 0.5 to 1.5 L; formed from aluminum; and in most cases are disposable. Disposable cylinders are non-refillable, thereby requiring disposal of the cylinder as hazardous waste. Typically, the customer is responsible for handling the disposal of the cylinder.
The compressed gas cylinder typically has a valve for filling, containing the pressurized gas in the cylinder, and releasing the pressurized gas from the cylinder. The outlet of this valve has a standard thread. One example is a ⅝″-18 UNF-2B thread commonly referred to as a “C-10 valve”. A standard C-10 valve has a single cylinder connection point which mates with the C-10 valve to the cylinder. This connection is typically a straight thread (e.g. ¾″-16-UNF 2A) and makes a seal to the cylinder via an o-ring. C-10 valves have been widely used in the field strictly as an on-off valve for the delivery of gases from compressed gas cylinders. In the closed position, the C-10 valve prevents flow of gas from the cylinder, and in the open position, the C-10 valve moves to the open position to allow the gas to dispense from the cylinder. The gas is delivered at cylinder pressure.
Because the C-10 valve does not regulate pressure, but rather solely functions as an on-off valve, a pressure regulator is required to down regulate the pressure from the cylinder pressure to the delivery pressure required by the end user (e.g., analyzer), which is generally 30-35 psig. The pressure regulator is connected to the C-10 valve; the pressure regulator has a complimentary thread of ⅝″-18 UNF-2A on its inlet so it can be threaded onto the C-10 valve outlet. The connection from the gas analyzer to the compressed gas cylinder via the C-10 valve, which is connected to the pressure regulator, has become the standard in the industry today.
Today, the pressure regulators in the field that are used for these gas analyzer calibration applications are rated for a maximum inlet pressure of no more than 500-1000 psig. Consequently, although the C-10 valve is capable of handling a higher pressure and the cylinder is capable of handling a maximum fill pressure of 1800-2000 psig, the fill pressure is limited to the maximum inlet of the pressure regulator of no more than 500-1000 psig to avoid over pressurizing the pressure regulator. Because the cylinder package contents are limited by this pressure, only 25-50% of the cylinder capacity is being utilized. This underutilization of the cylinder volume capacity results in more frequent cylinder replacement; additional ordering and inventory requirements for both the supplier and the customer, and in the case of disposable cylinders, the creation of more disposable waste, which must be handled by the customer. The overall result is a potentially significant increase in wasted resources.
One alternative for a method of increasing the fill pressure in the cylinder and maintaining the rated outlet pressure of the C-10 valve is to replace the historically used pressure regulators that require no more than 500-1000 psig with a pressure regulating device that can receive cylinder pressure from the C-10 valve and then step down the cylinder pressure to the desired use pressure (e.g., 30-35 psig for a gas analyzer). This enables the users to fill the cylinders to a higher pressure and regulate the delivery pressure to a desired value as needed by the end user. Unfortunately, these external pressure regulating devices are bulky and add dimensional limitations to the use of C-10 valve cylinder package (i.e., compressed gas cylinder containing calibration gas and C-10 valve), which is required to be small in size, lightweight and portable for onsite usage at various locations in a plant. As such, the external regulating device may not be suitably compatible with the C-10 valve cylinder package.
An alternative C-10 valve has been proposed by Lammers (US Patent Publication No. 2015/0013776 A1), who has attempted to integrate the regulating function within the C-10 valve. A representative schematic of the Lammers valve is shown in FIG. 2b. Lammers describes a regulating C-10 valve 205 containing a regulating function, whereby the gas pressure from the cylinder is reduced to approximately 900 psig along with the same on-off functions of the standard C-10 valve 201 shown in FIG. 2a. However, Lammers suffers from limitations. In particular, FIG. 2b shows that the regulating C-10 valve 205 requires the use of an external separate fill port 730 to bypass the regulator 702 during the cylinder filling process. The additional fill port 730 adds complexity, cost and another potential gas leak path to the regulating C-10 valve 205. The regulating C-10 valve 205 of Lammers significantly increases the exposed height of the C-10 valve body above the threaded region that threads into the top of the cylinder. Specifically, while a standard C-10 valve 201 (FIG. 201) has an exposed height of 0.5 inches above the threads, the regulating C-10 valve 205 of Lammers has an exposed height of 2.5 inches above the threaded region that threads into the top of the cylinder. The result is a bulky regulating C-10 valve 205 and cylinder package that can be too large to use for certain applications having space-constrained areas, such as, by way of example, industrial hygiene and EPA emission applications. This may provide dimensional limitations during the use of this device.
Further, the regulating C-10 valve 205 of Lammers is also deficient as it requires a separate fill port 730 in addition to the use port 753. The separate fill port 730 necessitates special equipment for modified drying, evacuation and filling of the cylinder, all of which are required steps when preparing cylinder packages. The special processing equipment requires implementing specialized fittings and connections to be installed on the cylinder during drying, evacuating and filling. Subsequently, the equipment, fitting and connections must be removed upon completion of drying, evacuating and filling. These additional steps undesirably increase time and complexity of preparing the cylinder packages.
Other methods for down regulating a pressure do not involve a C-10 connection but rather a regulator or series of regulators located inside the cylinder, as disclosed in U.S. Pat. Nos. 6,089,027 and 6,101,816. However, such a design suffers from the same drawbacks as the modified C-10 valve of Lammers, namely the need for a separate fill port for filling the cylinder.
In view of these drawbacks, there is an unmet need for an improved C-10 valve that allows greater utilization of cylinder capacity; simplifies filling and dispensing; and allows for regulating gas pressure during delivery without increasing the overall size of the cylinder package.